Method and apparatus for wireless resource allocation for relay in wireless communication system

ABSTRACT

A method of allocating a radio resource for a relay station in a wireless communication system is disclosed. The method comprise allocating a relay zone to the relay station in a subframe and transmitting a relay control channel to the relay station by using the relay zone, wherein the subframe comprises a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and a plurality of subcarriers in a frequency domain, wherein the subframe is divided into a user zone used by a user equipment in a cell and the relay zone used by the relay station, and wherein the relay zone comprises some of the plurality of subcarriers. According to the present invention, a subframe structure provides backward compatibility with a legacy wireless communication system. A relay station can effectively find a radio resource allocated to the relay station, thereby decreasing a decoding time.

TECHNICAL FIELD

The present invention relates to wireless communications, and moreparticularly, to designing of a subframe structure ensuring backwardcompatibility in a wireless communication system and communication usingthe subframe structure.

BACKGROUND ART

Standardization works of international mobile telecommunication(IMT)-advanced which is a next generation (i.e., post 3^(rd) generation)mobile communication system are carried out in the internationaltelecommunication union radio communication sector (ITU-R). TheIMT-advanced aims at support of an Internet protocol (IP)-basedmultimedia service with a data transfer rate of 1 Gbps in a stationaryor slowly moving state or 100 Mbps in a fast moving state.

3^(rd) generation partnership project (3GPP) is a system standardsatisfying requirements of the IMT-advanced, and prepares LTE-advancedwhich is an improved version of long term evolution (LTE) based onorthogonal frequency division multiple access (OFDMA)/singlecarrier-frequency division multiple access (SC-FDMA) transmission. TheLTE-advanced is one of promising candidates for the IMT-advanced.

The LTE-advanced (LTE-A) may include a new technology, e.g., relay,coordinated multiple point transmission/reception (CoMP), etc., and cansupport an improved technology, e.g., multiple input multiple output(MIMO) extension which uses a more number of transmit antennas than thenumber of transmit antennas used in the LTE. A relay station is a devicefor relaying a signal between a base station and a user equipment, andis used for cell coverage extension and throughput enhancement of awireless communication system.

Backward compatibility with a user equipment, a network, or the likewhich is designed to operate in the legacy LTE is one of factors to beconsidered in the LTE-A. That is, the LTE-A preferably supportsoperations of the user equipment, the network, or the like which isdesigned to operate in the LTE. From this aspect, designing of asubframe structure, that is, allocation of radio resources in asubframe, is a matter to be considered.

In addition, the relay station decodes a physical downlink controlchannel (PDCCH) allocated to the relay station by performing blinddecoding in a radio resource region allocated in a subframe. Further,the relay station receives data by finding a physical downlink sharedchannel (PDSCH) allocated to the relay station through the PDCCH.However, it is ineffective to perform blind decoding by the relaystation throughout a full frequency band in a frequency domain of asubframe.

Accordingly, there is a need for a subframe structure and a methodcapable of effectively allocating radio resources to a relay stationwhile providing backward compatibility with a legacy user equipment in awireless communication system employing the relay station.

DISCLOSURE Technical Problem

The present invention provides a method and apparatus for allocatingradio resources for a subframe, whereby the radio resources can beeffectively allocated to a relay station while providing backwardcompatibility in a wireless communication system employing the relaystation.

Technical Solution

According to an aspect of the present invention, a method of allocatinga radio resource for a relay station in a wireless communication systemis provided. The method includes allocating a relay zone to the relaystation in a subframe, and transmitting a relay control channel to therelay station by using the relay zone, wherein the subframe comprises aplurality of orthogonal frequency division multiplexing (OFDM) symbolsin a time domain and a plurality of subcarriers in a frequency domain,wherein the subframe is divided into a user zone used by a userequipment in a cell and the relay zone used by the relay station, andwherein the relay zone comprises some of the plurality of subcarriers.

According to another aspect of the present invention, a method ofmonitoring a control channel of a relay station in a wirelesscommunication system is provided. The method includes detecting thecontrol channel by monitoring the control channel in a subframe, andreceiving data of the relay station through a data channel indicated bya radio resource allocation of the control channel detected in thesubframe, wherein the subframe is divided into a user zone used by auser equipment in a cell and a relay zone used by the relay station, andwherein the relay station monitors the control channel in the relayzone.

Advantageous Effects

According to the present invention, a subframe structure providesbackward compatibility with a legacy wireless communication system. Arelay station can effectively find a radio resource allocated to therelay station, thereby decreasing a decoding time.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows a wireless communication system employing a relay station.

FIG. 3 shows a frequency division duplex (FDD) radio frame structure ofa 3^(rd generation partnership project ()3GPP) long term evolution (LTE)system.

FIG. 4 shows a time division duplex (TDD) radio frame structure of a3GPP LET system.

FIG. 5 shows an example of a resource grid for one slot.

FIG. 6 shows an example of a downlink subframe structure used in 3GPPLTE.

FIG. 7 shows downlink data transmission in 3GPP LTE.

FIG. 8 shows a subframe structure according to an embodiment of thepresent invention.

FIG. 9 shows an example of a relay zone in a subframe in which a size ofa control region is 1.

FIG. 10 shows an example of a relay zone in a subframe in which a sizeof a control region is 2.

FIG. 11 shows an example of a relay zone in a subframe in which a sizeof a control region is 3.

FIG. 12 shows an example of a relay zone in a subframe in which a sizeof a control region is 1.

FIG. 13 shows an example of a relay zone in a subframe in which a sizeof a control region is 2.

FIG. 14 shows an example of a relay zone in a subframe in which a sizeof a control region is 3.

FIG. 15 shows a subframe structure when an access control region has adifferent size.

FIG. 16 shows an example of allocating a control relay zone in a relayzone.

FIG. 17 shows an example of allocating a relay zone.

FIG. 18 shows an example of allocating a relay zone.

FIG. 19 shows an example of allocating a primary broadcast channel(PBCH) for an LTE-advanced (LTE-A) user equipment (UE) by performingfrequency division multiplexing (FDM) on the PBCH with a physicaldownlink shared channel (PDSCH) for an LTE UE.

FIG. 20 shows an example of allocating a PBCH for an LTE-A UE in acontrol region of the LTE-A UE.

FIG. 21 shows an example of allocating a shared channel (SCH) and a PBCHfor an LTE-A UE.

FIG. 22 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention.

MODE FOR INVENTION

3^(rd) generation partnership project (3GPP) long term evolution (LTE)is a part of evolved-universal mobile telecommunications system(E-UMTS). The 3GPP LTE employs orthogonal frequency division multipleaccess (OFDMA) in a downlink and employs single carrier-frequencydivision multiple access (SC-FDMA) in an uplink. LTE-advanced (LTE-A) isan evolution of LTE. An LTE system is a system based on 3GPP TS release8. An LTE-A system has backward compatibility with the LTE system.

For clarity of explanation, the following description will focus on 3GPPLTE/LTE-A. However, the technical features of the present invention arenot limited thereto. Hereinafter, an LTE user equipment (UE) is a UEsupporting LTE, and an LTE-A UE is a UE supporting LTE and/or LTE-A.However, this is for exemplary purposes only, and thus the LTE UE may bea first UE supporting a first radio access technology (RAT), and theLTE-A UE may be a second UE supporting not only the first RAT but also asecond RAT providing backward compatibility with the first RAT.

FIG. 1 shows a wireless communication system.

Referring to FIG. 1, a wireless communication system 10 includes atleast one base station (BS) 11. Each BS 11 provides a communicationservice to a specific geographical region 15 generally referred to as acell. The cell can be divided into a plurality of regions, and eachregion can be referred to as a sector. The BS 11 is generally a fixedstation that communicates with a user equipment (UE) 12 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc. The BS 11 canperform functions such as connectivity with the UE 12, management,control, resource allocation, etc.

The UE 12 may be fixed or mobile, and may be referred to as anotherterminology, such as a mobile station (MS), a user terminal (UT), asubscriber station (SS), a wireless device, a personal digital assistant(PDA), a wireless modem, a handheld device, etc. Hereinafter, a downlink(DL) implies communication from the BS 11 to the UE 12, and an uplink(UL) implies communication from the UE 12 to the BS 11.

FIG. 2 shows a wireless communication system employing a relay station.A relay station (RS) 16 is a device for relaying a signal between a BS11 and an MS 14, and is also referred to as another terminology such asa relay node (RN), a repeater, a relay, etc.

An MS can be classified into a macro UE (or simply Ma_UE) 13 and a relayUE (or simply Re_UE) 14. The Ma_UE 13 denotes a UE which directlycommunicates with the BS 11. The Re_UE 14 denotes a UE whichcommunicates with the RS. Even if the Ma_UE 13 is located in a cell ofthe BS 11, the Ma_UE 13 can communicate with the BS 11 via the RS 16 toimprove a transfer rate based on a diversity effect. The Ma_UE 13 and/orthe Re_UE 14 may include an LTE UE or an LTE-A UE.

Hereinafter, a backhaul link denotes a link between the BS 11 and the RS16. A backhaul downlink denotes communication from the BS 11 to the RS16. A backhaul uplink denotes communication from the RS 16 to the BS 11.An access link denotes a link between the RS 16 and the Re_UE 14. Anaccess downlink denotes communication from the RS 16 to the Re_UE 14. Anaccess uplink denotes communication from the Re_UE 14 to the RS 16.

FIG. 3 shows a frequency division duplex (FDD) radio frame structure ofa 3GPP LET system. The sector 4.1 of 3GPP TS 36.211 (V8.4.0)“TechnicalSpecification; Evolved Universal Terrestrial Radio Access (E-UTRA);Physical Channels and Modulation (Release 8)” may be incorporated hereinby reference. When in an FDD mode, DL transmission and UL transmissionare divided in a frequency domain.

Referring to FIG. 3, a radio frame consists of 10 subframes, and onesubframe consists of two slots. For example, one subframe may have alength of 1 millisecond (ms), and one slot may have a length of 0.5 ms.The slot may consist of 7 orthogonal frequency division multiplexing(OFDM) symbols in case of a normal cyclic prefix (CP), and may consistof 6 OFDM symbols in case of an extended CP. Therefore, a normalsubframe having the normal CP may include 14 OFDM symbols, and anextended subframe having the extended CP may have 12 OFDM symbols.

FIG. 4 shows a time division duplex (TDD) radio frame structure of a3GPP LTE system. The section 4.2 of 3GPP TS 36.211 (V8.4.0) may beincorporated herein by reference.

Referring to FIG. 4, a radio frame consists of two half-frames. Thehalf-frame consists of five subframes.

A UL and a DL are identified in a subframe unit. A UL subframe and a DLsubframe are separated by a switching point. The switching point is aregion for separating the UL and the DL between the UL subframe and theDL subframe. The radio frame has at least one switching point. Theswitching point includes a downlink pilot time slot (DwPTS), a guardperiod (GP), and an uplink pilot time slot (UpPTS). The DwPTS is usedfor initial cell search, synchronization, or channel estimation. TheUpPTS is used for channel estimation in a BS and for UL transmissionsynchronization of a UE. The GP is a guarding duration for removinginterference generated in the UL due to a multi-path delay of a DLsignal between the UL and the DL.

The radio frame structure of FIG. 3 and FIG. 4 is for exemplary purposesonly, and thus the number of subframes included in the radio frame orthe number of slots included in the subframe may change variously.

FIG. 5 shows an example of a resource grid for one slot.

Referring to FIG. 5, a slot (e.g., a DL slot included in a DL subframe)includes a plurality of OFDM symbols in a time domain. It is describedherein that one DL slot includes 7 OFDMA symbols and one resource blockincludes 12 subcarriers in a frequency domain for exemplary purposesonly, and the present invention is not limited thereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberN^(DL) of resource blocks included in the DL slot depends on a DLtransmission bandwidth determined in a cell.

In the 3GPP LTE, the resource block is classified into a physicalresource block (PRB) and a virtual resource block (VRB). The PRBincludes N^(DL) _(symb) OFDM symbols in the time domain and N^(RB) _(sc)subcarriers in the frequency domain. N^(DL) _(symb) denotes the numberof OFDM symbols included in one slot, and N^(RB) _(sc) denotes thenumber of subcarriers included in one resource block. The PRB is indexedfrom 0 to (NDL_(RB)−1) in the frequency domain. N^(DL) _(RB) denotes atotal number of resource blocks depending on a DL bandwidth. In thefrequency domain, a VRB index n_(PRB) is related with a resource element(k,l) as expressed by the following equation.

$\begin{matrix}{n_{PRB} = \left\lfloor \frac{k}{N_{sc}^{RB}} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

The VRB has the same size as the PRB, and is classified into a localizedtype and a distributed type. The localized-type VRB is directly mappedto the PRB so that a VRB n_(VRB) corresponds to a PRB n_(PRB).

The distributed-type VRB is mapped to the PRB in the following manner.First, a parameter N_(gap) is given by the following table.

TABLE 1 Gap (N_(gap)) 1^(st) Gap 2^(nd) Gap System BW (N_(RB) ^(DL))(N_(gap,1)) (N_(gap,2))  6-10 ┌N_(RB) ^(DL)/2┐ N/A 11 4 N/A 12-19 8 N/A20-26 12 N/A 27-44 18 N/A 45-49 27 N/A 50-63 27 9 64-79 32 16  80-110 4816

Whether N_(gap) is N_(gap,1) or N_(gap,2) is reported by a BS to a UE asa part of a downlink grant.

The VRB is indexed from 0 to (N^(DL) _(VRB)−1). N^(DL) _(VRB) denotesthe number of VRBs, and is determined based on N_(gap). According to aVRB index, the VRB is interleaved again. The sector 6.2.3.2 of 3GPP TS36.211 (V8.4.0) may be incorporated herein by reference for furtherdetails of mapping from the VRB to the PRB.

A resource block denotes a PRB hereinafter unless otherwise specified.

FIG. 6 shows an example of a downlink subframe structure used in 3GPPLTE.

Referring to FIG. 6, a subframe includes two slots. A maximum of threepreceding OFDM symbols of a 1^(st) slot in a subframe correspond to acontrol region to be allocated with control channels. The remaining OFDMsymbols correspond to a data region to be allocated with a physicaldownlink shared channel (PDSCH).

Examples of downlink control channels used in the LTE include a physicalcontrol format indicator channel (PCFICH), a physical hybrid-ARQindicator channel (PHICH), a physical downlink control channel (PDCCH),etc. The PCFICH transmitted in a 1^(st) OFDM symbol of a subframecarries information regarding the number of OFDM symbols (i.e., a sizeof a control region) used for transmission of control channels in thesubframe.

The PHICH carries an acknowledgement (ACK)/not-acknowledgement (NACK)signal for an uplink hybrid automatic repeat request (HARQ). That is,the ACK/NACK signal for uplink data transmitted by a UE is transmittedover the PHICH. A PHICH duration denotes the number of OFDM symbols thatcan be used in PHICH transmission.

The PDCCH can carry a downlink shared channel (DL-SCH)'s resourceallocation and transmission format, uplink shared channel (UL-SCH)'sresource allocation information, paging information over a pagingchannel (PCH), system information on a DL-SCH, a resource allocation ofa higher layer control message such as a random access responsetransmitted over a PDSCH, a transmit power control command forindividual UEs included in any UE group, activation of a voice overInternet (VoIP), etc. A plurality of PDCCHs can be transmitted in acontrol region, and the UE can monitor the plurality of PDCCHs. ThePDCCH is transmitted over an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate depending on a radiochannel condition. The CCE corresponds to a plurality of resourceelement groups. According to an association relation between the numberof CCEs and a coding rate provided by the CCEs, a format of the PDCCHand the number of bits of an available PDCCH are determined. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI indicates uplink resource allocationinformation (or referred to as an uplink grant), downlink resourceallocation information (or referred to as a downlink grant), an uplinktransmit power control command for any UE groups, etc.

The following table shows the DCI according to a DCI format.

TABLE 2 DCI Format Description DCI format 0 used for the scheduling ofPUSCH DCI format 1 used for the scheduling of one PDSCH codeword DCIformat 1A used for the compact scheduling of one PDSCH codeword andrandom access procedure initiated by a PDCCH order DCI format 1B usedfor the compact scheduling of one PDSCH codeword with precodinginformation DCI format 1C used for very compact scheduling of one PDSCHcodeword DCI format 1D used for the compact scheduling of one PDSCHcodeword with precoding and power offset information DCI format 2 usedfor scheduling PDSCH to UEs configured in closed- loop spatialmultiplexing mode DCI format 2A used for scheduling PDSCH to UEsconfigured in open-loop spatial multiplexing mode DCI format 3 used forthe transmission of TPC commands for PUCCH and PUSCH with 2-bit poweradjustments DCI format 3A used for the transmission of TPC commands forPUCCH and PUSCH with single bit power adjustments

A DCI format 0 indicates uplink resource allocation information. DCIformats 1 to 2 indicate downlink resource allocation information. DCIformats 3 and 3A indicate an uplink transmit power control (TPC) commandfor any UE groups.

The BS determines a PDCCH format according to the DCI to be sent to theUE, and attaches a cyclic redundancy check (CRC) to the DCI. The CRC ismasked with a unique identifier (referred to as a radio networktemporary identifier (RNTI)) according to an owner or a usage. If aPDCCH is for a specific UE, a unique identifier of the UE, e.g.,cell-RNTI (C-RNTI), may be masked to the CRC.

A search space is defined as a space for searching for a PDCCH in acontrol region. A set of PDCCH candidates to be monitored is definedbased on the search space. When an aggregation of all CCEs for the PDCCHis defined as a CCE aggregation in one subframe, the search space is anaggregation of contiguous CCEs beginning at a specific start point inthe CCE aggregation according to a CCE aggregation level. The CCEaggregation level is a CCE unit for searching for the PDCCH, and a sizethereof is defined by the number of contiguous CCEs. The CCE aggregationlevel denotes the number of CCEs used for transmission of the PDCCH. Thesearch space is defined according to the CCE aggregation level. Aposition of each PDCCH candidate differs in the search space accordingto each CCE aggregation level.

The search space can be classified into a common search space and aUE-specific search space. The common search space is monitored by allUEs within a cell. The UE-specific search space is monitored by aspecific UE. A UE monitors the common search space and/or theUE-specific search space according to control information to bereceived. The number of CCE aggregation levels supported by the commonsearch space is less than the number of CCE aggregation levels supportedby the UE-specific search space. The common search space and theUE-specific search space may overlap with each other.

FIG. 7 shows downlink data transmission in 3GPP LTE. A UE receivesdownlink data over a PDSCH 96 indicated by a PDCCH 92. The UE monitorsthe PDCCH 92 in a downlink subframe, and receives a downlink resourceallocation over the PDCCH 92. The UE receives downlink data over thePDSCH 96 indicated by the downlink resource allocation.

According to Table 2, DCI formats 1, 1A, 1B, 1C, 1D, 2, and 2A areexamples of a DCI format including the downlink resource allocation. TheUE interprets a resource allocation based on the detected DCI format.

According to the section 7.1.6 of 3GPP TS 36.213 (V8.4.0) incorporatedherein by reference, three types of resource allocations are providedbased on the DCI format The DCI formats 1, 2, and 2A use a resourceallocation type 0 or 1. The DCI format 1A, 1B, 1C, and 1D use a resourceallocation type 2. Whether the resource allocation type is 0 or 1 isdetermined by a resource allocation field included in a PDCCH.Therefore, the DCI formats 1A, 1B, 1C, and 1D using only the resourceallocation type 2 do not have the resource allocation field.

The resource allocation type 0 includes a bitmap indicating a resourceblock group (RBG) allocated to the UE. The RBG is a set of contiguousPRBs. An RBG size P depends on a system bandwidth. A total numberN_(RBG) of RBGs is given by N_(RBG)=N^(DL) _(RB)/P. The resourceallocation type 1 indicates an RBG allocated to the UE from a PRB setselected from one of P RBG subsets. That is, the resource allocationtype 0 reports an RBG allocated to the UE among from all RBGs as anabsolute position value. The resource allocation type 1 divides all RBGsinto a plurality of subsets, and reports an RBG allocated to the UEwithin a subset. The resource allocation type 2 indicates a plurality ofcontiguous VRBs allocated to the UE. The DCI formats 1A, 1B, 1C, and 1Dinclude a 1-bit flag indicating a localized-type VRB or adistributed-type VRB.

<Relay Zone Allocation Method>

FIG. 8 shows a subframe structure according to an embodiment of thepresent invention.

Referring to FIG. 8, a subframe includes N (e.g., 12 or 14) OFDM symbolsin a time domain. The subframe includes a control region 110 and a dataregion 120 to support a legacy 3GPP LTE UE and/or a legacy 3GPP LTE-AUE. Hereinafter, a macro UE denotes a UE supporting a 3GPP LTE and/or a3GPP LTE-A which directly receive a service from a BS. In addition, thesubframe includes relay zones 130 and 140 to support an RS. That is, therelay zone 130 and 140 are defined as certain regions which areallocated with a radio resource for performing relaying in the existingdata region. Although two relay zones 130 and 140 are shown herein forexample, the number of relay zones in the subframe is not limitedthereto.

The control region 110 may include M preceding OFDM symbols out of NOFDM symbols. The relay zones 130 and 140 may include P OFDM symbolsspaced apart fully or partially by one OFDM symbol from the controlregion 110. Herein, 0<P<(N−M). Therefore, the control region 110 and therelay zones 130 and 140 are divided in the time domain, which isreferred to as time division multiplexing (TDM).

The relay zones 130 and 140 may be divided in a frequency domain in asubframe. That is, the first relay zone 130 and the second relay zone140 occupy different frequencies (or subcarriers). That is, when asubframe includes a plurality of subcarriers in the frequency domain,the relay zones 130 and 140 include OFDM symbols excluding at least onepreceding OFDM symbol among N OFDM symbols and include some subcarriersamong the plurality of subcarriers. That is, the relay zones 130 and 140are divided in the frequency domain, which is referred to as frequencydivision multiplexing (FDM).

The relay zone 130 includes a control relay zone 132 and a data relayzone 134. The control relay zone 132 may include at least one precedingOFDM symbol within the relay zone 130. A size of the control relay zone132 (i.e., the number of OFDM symbols included in the control relay zone132) is not limited to any specific value, and thus may be fixed or varydepending on a system. When the size of the control relay zone 132varies, the size may be reported by using the existing PCFICH, or may bereported by using a part of system information or an additional channelin the relay zone 130.

A control channel for the RS (referred to as an R-PDCCH) may betransmitted in the control relay zone 132. A data channel for the RS(referred to as an R-PDSCH) may be transmitted in the data rely zone134. The R-PDCCH may carry a backhaul downlink radio allocation for theRS and a backhaul uplink radio allocation for the RS. The R-PDSCHcarriers relay data for the RS (also referred to as a transport block,an information bit, or a data packet). The backhaul downlink radioresource allocation in the R-PDCCH indicates an R-PDSCH resource of anRS scheduled in the data relay zone. The RS receives a transport blockover the R-PDSCH indicated by the backhaul downlink radio resourceallocation received over the R-PDCCH. The RS may receive a controlchannel allocated to the RS by using a method of monitoring the controlrelay zone 132 included in the relay zone 130.

The control relay zone 132 and the data rely zone 134 are not includedin all relay zones. A certain relay zone may include only a controlrelay zone, and another relay zone may include only a data relay zone.

A subframe in which the relay zones 130 and 140 are included may be apart of 10 subframes constituting a radio frame. A position of thesubframe in which the relay zones 130 and 140 are included may bereported by the BS to the RS by using a part of system information,higher layer signaling, and/or the PDCCH.

Hereinafter, the relay zone is described as a radio resource region usedwhen the BS receives data from the RS. However, the relay zone may beused when the BS transmits data to an LTE-A UE or when the BS receivesdata from the LTE-A UE. That is, in the subframe, the existing controlregion and the existing data region are regions providing backwardcompatibility with an LTE UE, and the relay zone is a region notsupporting backward compatibility. The control region and the dataregion which are used to provide backward compatibility with the LTE UEare referred to as legacy zone or user zone. In the relay zone, the LTEUE may not perform any channel estimation. For clarity of explanation,the relay zone is used dedicatedly by the RS in the followingdescription. However, the present invention can also apply to a casewhere the relay zone is used dedicatedly by the LTE-A UE or shared bythe RS, which is apparent to those skilled in the art.

As described above, in the subframe structure of the legacy 3GPP LTE, asize of the control region 110 is indicated by the PCFICH, and the sizemay be 1, 2, or 3 OFDM symbols. Hereinafter, allocation of the relayzone will be described in detail according to the size of the controlregion.

First, a region for transmitting a PDCCH by an RS to a relay UE managedby the RS is necessary in a subframe. Such a region is referred to as anaccess control region. That is, the RS transmits the PDCCH to the relayUE during a time when a BS transmits the PDCCH to a macro UE in thesubframe. In addition, in order for the RS to receive again signal inrelay zone after transmitting the PDCCH to the relay UE, physicalswitching from radio frequency (RF) transmission to RF reception isnecessary. A guard time (GT) or a transition time is required to ensurea time for such switching.

First, assume that the access control region corresponds to twopreceding OFDM symbols of a subframe, and the GT corresponds to one OFDMsymbol. FIG. 9 shows an example of a relay zone in a subframe in which asize of a control region is 1. FIG. 10 shows an example of a relay zonein a subframe in which a size of a control region is 2. FIG. 11 shows anexample of a relay zone in a subframe in which a size of a controlregion is 3. A BS transmits a PDCCH to a macro UE (i.e., an LTE UEand/or an LTE-A UE) in a control region 180. Relay zones 190 and 200include 4^(th) through last OFDM symbols of a subframe. Since a size ofthe access control region is 2 and the GT occupies one OFDM symbol, therelay zone starts from the 4^(th) OFDM symbol in any case.

Second, assume that the access control region corresponds to onepreceding OFDM symbol of a subframe, and the GT corresponds to one OFDMsymbol. FIG. 12 shows an example of a relay zone in a subframe in whicha size of a control region is 1. FIG. 13 shows an example of a relayzone in a subframe in which a size of a control region is 2. FIG. 14shows an example of a relay zone in a subframe in which a size of acontrol region is 3. The relay zone includes 3^(rd) through last OFDMsymbols of a subframe. Since a size of the access control region is 1and the GT occupies one OFDM symbol, the relay zone starts from the3^(rd) OFDM symbol in any case.

Meanwhile, a size or position of the access control region and/or a sizeof the GT may differ for each RS. FIG. 15 shows a subframe structurewhen an access control region has a different size. A first relay zone210 starts from a 4^(th) OFDM symbol, and a second relay zone 220 startsfrom a 3^(rd) OFDM symbol. That is, the first relay zone 210 includes anaccess control region having a size of 2, and is allocated to an RS ofwhich a GT occupies one OFDM symbol. The second relay zone 220 includesan access control region having a size of 1, and is allocated to an RSof which a GT occupies one OFDM symbol. Therefore, the BS can regulate aposition or size of a relay zone allocated according to a GT or anaccess control region supported by the RS.

Although it has been described above that the size of the control relayzone included in the relay zone (i.e., a region for transmitting anR-PDCCH) is one OFDM symbol for example with reference to FIG. 9 to FIG.15, the present invention is not limited thereto.

FIG. 16 shows an example of allocating a control relay zone in a relayzone. A relay zone 240 includes a control relay zone 242 and a datarelay zone 246. The control relay zone 242 includes two separate zones242 a and 242 b. The first zone 242 a includes a 4^(th) OFDM symbol, andthe second zone 242 b includes a 13^(th) OFDM symbol. However, positionsor the number of OFDM symbols included in each zone is for exemplarypurposes only. The first zone 242 a and the second zone 242 b maytransmit different control channels. The first zone 242 a temporallyprior to the second zone 242 b may transmit a PDCCH and a PCFICH, andthe second zone 242 b may transmit a PHICH. Alternatively, the firstzone 242 a may transmit a PDCCH for carrying a backhaul downlinkresource allocation, and the second zone 242 b may transmit a PDCCH forcarrying a back uplink radio allocation.

As shown in FIG. 8 to FIG. 16 above, the relay zone may be configured invarious formats. To configure the relay zone, configuration informationis required to indicate a start point of the relay zone, a size of therelay zone, a size of the control relay zone, and/or a format of thecontrol relay zone. The configuration of the relay zone may be fixed ormay change with a specific period. That is, a format or size of therelay zone may be fixed in each configured subframe or may change with aspecific period. Alternatively, relay zone configuration information maybe reported by a BS to an RS by using a part of system information, ahigher layer message such as a radio resource control (RRC) message,and/or an R-PDCCH. The relay zone configuration information may bepiggyback transmitted on a transport block.

Now, backhaul downlink resource allocation over an R-PDCCH will bedescribed. By using the backhaul downlink resource allocation, an RSreceives an R-PDSCH. As described above, the 3GPP LTE configures aresource allocation based on a PRB or a VRB.

FIG. 17 shows an example of allocating a relay zone. A relay zoneindication unit (RZIU) 250 is a resource allocation unit for indicatingallocation of a relay zone, and includes at least one PRB. A size of theRZIU can be expressed by (N_(PRB)/N_(RZIU)) in a frequency domain.Herein, N_(PRB) denotes the number of all PRBs included in a frequencyband of a subframe, and N_(RZIU) denotes the number of RZIUs included inthe frequency band of the subframe. A BS may report N_(RZIU) to an RS.

For relay zone allocation, the BS may report an RZIU allocated in abitmap format to a scheduled RS. That is, the RZIU is indexed from 0 to(N_(RZIU)−1), and a bitmap of the allocated RZIU is reported by the BSto the RS. Alternatively, the BS may report an index of an RZIU at whichthe relay zone starts and the number of included RZIUs and thus reportthe relay zone allocation to the scheduled RS. Alternatively, the BS mayreport an index of the RZIU at which the relay zone starts and an indexof a last RZIU and thus report the relay zone allocation to thescheduled RS.

FIG. 18 shows an example of allocating a relay zone. A subfigure (a)shows a subframe structure from the perspective of a BS. A subfigure (b)shows a subframe structure from the perspective of an RS. In thesubfigure (a) of FIG. 18, a PDCCH for a macro UE is transmitted in acontrol region 262. Further, in a region including 4^(th) through lastOFDM symbols, a relay zone 260 may be allocated in a unit of RZIU. Therelay zone is multiplexed by performing FDM in a PDSCH regiontransmitted to the macro UE. In the subfigure (b) of FIG. 18, the RStransmits a control channel such as a PDCCH to a relay UE in an accesscontrol region 272 and provides a GT in a 3^(rd) OFDM symbol. Then, theRS receives an R-PDCCH in a first relay zone 270 including OFDM symbolssubsequent to a 4^(th) OFDM symbol, and receives a transport blockthrough an R-PDSCH of a second relay zone 380 indicated by a detectedR-PDCCH.

Hereinafter, a primary broadcast channel (PBCH) for an LTE-A UE will bedescribed.

FIG. 19 shows an example of allocating a PBCH for an LTE-A UE byperforming FDM on the PBCH with a PDSCH for an LTE UE. A BS may allocatea specific PRB 390 of at least one subframe 380 among a plurality ofsubframes included in a radio frame to the PBCH for the LTE-A. The PBCHfor the LTE-A may undergo FDM with a PDSCH 400 for the LTE UE. The PBCHfor the LTE-A UE may be allocated in a unit of a multiple of the radioframe. For example, the PBCH may be allocated with a time interval suchas 10 ms, 20 ms, or 40 ms.

FIG. 20 shows an example of allocating a PBCH for an LTE-A UE in acontrol region of the LTE-A UE.

A BS may always determine at least one subframe among a plurality ofsubframes included in a radio frame as a subframe for the LTE-A UE, andallocate a PBCH (and/or a dynamic BCH) for the LTE-A to a specific OFDMsymbol (or a specific subcarrier) included in a control region 410 forthe LTE-A UE in the subframe. Preceding two (or one) OFDM symbols of asubframe 1 are allocated to a control region for an LTE UE for backwardcompatibility with LTE. Such a method can also apply to a PBCH for anRS.

FIG. 21 shows an example of allocating an SCH and a PBCH for an LTE-AUE.

A BS determines at least one subframe among a plurality of subframesincluded in a radio frame as a subframe for an LTE-A UE, and allocatesan LTE-A specific SCH 430 and an LTE-A specific PBCH 440 to a dataregion 420 included in the subframe. The LTE-A UE may perform an initialentry process in a cell by using the SCH 430 and the PBCH 440. Such amethod can also apply to an SCH and a PBCH for an RS.

When the PBCH for the LTE-A UE is allocated by using the methodsdescribed above with reference to FIG. 19 to FIG. 21, an RNTI of systeminformation for the LTE-A UE can be reported to the LTE-A UE by usingthe PBCH. Therefore, the LTE-A UE can achieve LTE-A specific dynamic BCHreception.

FIG. 22 is a block diagram showing a wireless communication systemaccording to an embodiment of the present invention. A BS 1500, an RS1530, and a UE 1550 perform communication through respective radiochannels.

The BS 1500 includes a processor 1501 and an RF unit 1502. The RF unit1502 transmits and/or receives a radio signal. The processor 1501 iscoupled to the RF unit 1502, and transmits data to the RS 1530. Theprocessor 1501 implements radio resource allocation and/or datatransmission/reception with respect to a subframe according to theaforementioned embodiments.

The RS 1530 includes a processor 1531 and an RF unit 1532. The RF unit1532 transmits and/or receives a radio signal. The processor 1531 iscoupled to the RF unit 1532, and relays data received from the BS 1500to the UE 1550. The processor 1531 implements datatransmission/reception depending on a subframe allocated according tothe aforementioned embodiments.

The UE 1550 includes a processor 1551 and an RF unit 1552. The RF unit1552 transmits and/or receives a radio signal. The processor 1551 iscoupled to the RF unit 1552. The processor 1551 receives data from theBS 1500 or the RS 1530, and demodulates and decodes the data.

The present invention can be implemented with hardware, software, orcombination thereof. In hardware implementation, the present inventioncan be implemented with one of an application specific integratedcircuit (ASIC), a digital signal processor (DSP), a programmable logicdevice (PLD), a field programmable gate array (FPGA), a processor, acontroller, a microprocessor, other electronic units, and combinationthereof, which are designed to perform the aforementioned functions. Insoftware implementation, the present invention can be implemented with amodule for performing the aforementioned functions. Software is storablein a memory unit and executed by the processor. Various means widelyknown to those skilled in the art can be used as the memory unit or theprocessor.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those skilled in the art that various changes in form and details maybe made therein without departing from the spirit and scope of theinvention as defined by the appended claims. The exemplary embodimentsshould be considered in descriptive sense only and not for purposes oflimitation. Therefore, the scope of the invention is defined not by thedetailed description of the invention but by the appended claims, andall differences within the scope will be construed as being included inthe present invention.

1. A method of allocating a radio resource for a relay station in awireless communication system, the method comprising: allocating a relayzone to the relay station in a subframe; and transmitting a relaycontrol channel to the relay station by using the relay zone, whereinthe subframe comprises a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in a time domain and a plurality ofsubcarriers in a frequency domain, wherein the relay zone comprises asubset of the plurality of OFDM symbols in the time domain and a portionof the plurality of subcarriers in the frequency domain, and whereinconfiguration information for the relay zone is provided by a higherlayer signal.
 2. The method of claim 1, wherein the configurationinformation for the relay zone comprises information of an OFDM symbolat which the relay zone begins.
 3. The method of claim 1, wherein therelay zone is allocated by a virtual resource block (VRB) unit in afrequency domain.
 4. A method of monitoring a control channel of a relaystation in a wireless communication system, the method comprising:detecting a relay control channel by monitoring the relay controlchannel in a subframe; and receiving data of the relay station through adata channel indicated by a radio resource allocation of the detectedrelay control channel, wherein the subframe comprises a plurality oforthogonal frequency division multiplexing (OFDM) symbols in a timedomain and a plurality of subcarriers in a frequency domain, wherein therelay control channel is monitored in a relay zone that comprises asubset of the plurality of OFDM symbols in the time domain and a portionof the plurality of subcarriers in the frequency domain, and whereinconfiguration information for the relay zone is provided by a higherlayer signal.
 5. The method of claim 1, wherein the relay controlchannel is transmitted from a fourth OFDM symbol in the subframe.